A hybrid vehicle may be propelled by an engine and an electric machine. In some examples, such a hybrid vehicle may additionally include a dual clutch transmission, which may utilize two separate clutches for odd and even gear sets. For any dual clutch transmission (DCT), the ability to precisely actuate clutch capacity is critical for drivability and shift quality. For example, it is important for a hybrid powertrain with a clutch or clutches for engine connection and disconnection, to be able to restart the engine and connect a disconnect clutch smoothly and quickly when the use of the engine is requested, to provide the requested torque and acceleration. Part-to-part variability and change over time are significant noise factors for clutch capacity control and estimation.
While there are examples of controlling dual clutch transmissions to find opportunities for clutch adaptation during transient operation involving non-intrusive schemes, such schemes adapt the clutch while the clutch is transmitting positive torque to the wheels. However, clutch adaptation for both positive and negative slip/torque is important for consistent operation and shift quality. Accordingly, there may be a need to improve schemes for clutch adaptation, particularly for hybrid vehicles that include a dual clutch transmission.
The inventors herein have recognized these issues, and have developed systems and methods to at least partially address them. In one example, a driveline operating method comprises adjusting values of a transfer function of a clutch of a dual clutch transmission in response to an operating condition of an engine and/or operating condition of an integrated starter/generator coupled to the engine while a vehicle is propelled via an electric machine coupled to the dual clutch transmission; and maintaining a driver demand wheel torque at vehicle wheels via adjusting torque of the electric machine in response to the operating condition of the engine and/or operating condition of the integrated starter/generator.
In an example of the method, the operating condition is a torque output or a current input, and where the electric machine supplies the driver demand wheel torque. In such an example, the method may further comprise applying the clutch according to the adjusted values of the transfer function.
In this way, a vehicle such as that described above may be controlled such that engine speed may be varied independently from wheel speed or an input shaft speed. In such a mode, the system may apply pressure to one of the clutches where engine speed is independently controlled to maintain positive or negative slip, thus enabling adaptation of positive and negative clutch transfer functions.
The present description may provide several advantages. For example, the approach may improve driveline efficiency. In addition, the approach may improve vehicle drivability by improving clutch control for connecting and disconnecting the engine from the driveline. For example, the approach may provide for consistent driveline operation and shift quality.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.